Hi Kerry --

Generally the rule of thumb for a post-treatment PET/CT scan seems to be about 3 months. This allows the worst of the inflammation to go down and healing to take place. There will still be some areas that will show activity (if it's a PET scan) and an experienced radiologist can usually (but not 100%) tell if it is due to normal healing (or perhaps, infection) rather than residual cancer.

If anything suspicious shows up, your doctor may order an MRI or wait a bit to see if there are changes, or -- if the area can be accessed easily, say base of tongue or tonsil -- do a biopsy. The ENT surgeon on my husband's team at Hopkins emphasizes that while fused PET/CT scans are very accurate, they are not 100% so, and not a substitute for a thorough physical exam (endoscope, etc.). A number of tools are used to assess response to treatment.

My husband, whose treatment ended Sept. 28 '05, has had two PET/CT scans and also several endoscopic and direct physical exams, and they have found no sign of cancer. He was Stage IV, base of tongue and tonsil, treated with 33x radiation (tomo-IMRT) and 7x chemo (carboplatin), no surgery save tonsillectomy prior to chemoradiation.

Gail